OLED (Organic Light-Emitting Diode) is active light emitting device. Compared with traditional LCD (Liquid Crystal Display) display, OLED display technology does not need backlight, which has a property of active light emitting. OLED uses a very thin layer of organic material and a glass substrate, and when a current is passed, the organic material will emit light. Therefore, the OLED display can significantly save energy, and can be made thinner and lighter, meanwhile withstanding a wider range of temperature changes than the LCD display, with a lager viewing angle. The OLED display is expected to become the next generation flat panel display technology after the LCD, and it is currently one of the most concerns in the flat panel display technology.
There are many methods for coloring OLED screen body. Currently, an OLED coloring technology which is more mature and has successful production is OLED evaporation technology which uses a traditional RGB stripe arrangement to evaporate. A side-by-side arrangement has the best picture effect. The side-by-side arrangement refers to an arrangement in which there are three sub-pixels in one pixel range: the red (R), green (G), and blue (B) sub-pixels. Each of the sub-pixels is a quadrilateral, and has an independent organic light emitting device. The organic light emitting device is formed on a corresponding pixel position on array substrate through fine metal mask (FMM) by evaporation coating film technology. The technical key of production of OLED screen body with high PPI (pixel per inch) is that the fine metal mask is fine and has good mechanical stability, and the key of the fine metal mask is an arrangement of the pixel and sub-pixel.
At present, in the art there are many arrangements such as slit, slot, pentile and IGNIS etc. However, the above arrangements can not well solve the problem of improving pixel density, for area of a mask opening has lower specification limit. Moreover, in order to avoid influence by tolerance during production process, there is a need to preset a gap between the openings for adjacent pixels, which makes it difficult for pixel density, e.g. PPI to be significantly improved, and pixel arrangement is not a real sense of the true color display and other reasons.
In the traditional pixel arrangement, each of the pixels is respectively composed of R, G, B three colors. In the pixel arrangement as shown in FIG. 1, one pixel is divided into R, G, B three parallel sub-pixels, and each of the sub-pixels is a quadrilateral. Size of the quadrilateral corresponding to the R, G, B sub-pixels is adjusted according to the property of corresponding RGB device. As shown in FIG. 1, a pixel region 100 includes an R sub-pixel region 101, an R light emitting region 102, a G sub-pixel region 103, a G light emitting region 104, a B sub-pixel region 105, and a B light emitting region 106. As illustrated, the area of the R, G, B sub-pixel regions is equal to that of the R, G, B light emitting regions, and the area can be adjusted as needed during implementation.
FIG. 1A and FIG. 1B respectively correspond to two evaporation masks of FIG. 1. Wherein, 107, 109 in FIG. 1A and FIG. 1B are mask occlusion area, evaporated region opening 108, 110 may be a slit or a slot.
FIG. 1A is a slit-type evaporation mask, and size of the corresponding metal mask opening corresponds to the size of the sub-pixel. A main characteristic of the opening type of the metal mask is that all the sub-pixels in the same column in the screen body share the same opening; the metal mask opening is longer in a length direction; with the display size increasing, the length of the metal mask opening also need to increase; and non-opening portions between adjacent openings forms a metal stripe.
For OLED screen body with low PPI, the slit-type opening makes spacing of the adjacent metal mask opening lager, the metal stripe wider, and the production and use of the metal mask easier. However, when the slit-type opening is applied into the OLED screen body with high PPI, the spacing between the adjacent fine metal mask opening becomes smaller, the metal stripe is thinner, and during use of the metal mask, the metal stripe is easy to deform under influence of direction of the magnetic induction line of magnet plate, resulting in different color materials of sub-pixels polluting with each other and color mixing, further leading to lower production yield. In addition, this kind of metal mask is also easily damaged deformed during use, cleaning, and storage process, therefore its recycling rate is not high. For higher cost of the metal mask, the cost of the screen body produced in this way is also higher.
FIG. 1B is a slot-type evaporation mask. A main characteristic of the opening type of the metal mask is that a bridge is added between pixels in the slit opening, in order to connect adjacent metal stripes, changing original one long opening to a plurality of opening units. This method makes the metal stripe of the metal mask more stable, solving the problem that the metal stripe with slit-type opening is easy to deform under influence of direction of the magnetic induction line of magnet plate. However, considering the long size precision of the metal mask, in order to avoid producing shadow effect to the sub-pixel during evaporation, enough distance must be kept between the sub-pixel and the bridge, leading to upper and lower length of the sub-pixels reduced, thereby impacting opening ratio of each sub-pixel.
In the above means, each opening in the mask can only correspond to one sub-pixel with the same color, of which the arrangement density can not be increased, and therefore the resolution can not be improved. Under affected by the technology level of mask, the opening in the mask can not be too small. Since the evaporation will produce “shadow effect”, a certain margin needs to be preset between two light emitting regions, to prevent the “shadow effect” from arising color mixing, therefore the mask opening can not be produced too small, otherwise will effect the opening ratio.
In the US patent application with publication number US20110128262 by Canada IGNIS company, an arrangement of pixel array is disclosed. However, each of the sub-pixels thereof is still quadrilateral, only the relative position relationship between the sub-pixels is different from the slit and slot arrangements, and the arrangement of three sub-pixels is shown in FIG. 2. A pixel region 200 includes an R sub-pixel region 201, an R light emitting region 202, a G sub-pixel region 203, a G light emitting region 204, a B sub-pixel region 205, and a B light emitting region 206. FIG. 2A and FIG. 2B respectively corresponds to two evaporation masks for the B sub-pixel shown in FIG. 2, and FIG. 2C corresponds to the evaporation mask for the R sub-pixel or the G sub-pixel. The mask opening is equivalent to dividing one pixel into two sub-pixels, and shadow regions 207, 209 and 211 as shown are respectively evaporated occlusion regions. Evaporated openings 208 and 210 for evaporating the B sub-pixel may be silt or slot, evaporated opening 212 is the mask opening for the R or G sub-pixel, and the evaporated opening still corresponds to one sub-pixel, that is, its length and width dimensions is equivalent to length and width dimensions of one sub-pixel. In this way, periodically horizontal and vertical translation of the pixel forms pixel array of rows and columns. The spacing between the metal mask openings corresponding to the red and green sub-pixels is relatively large, which can achieve high PPI display to some extent.
Pixels arranged periodically cause blue sub-pixels in the pixel array form a linear arrangement, which makes it necessary for the corresponding metal mask to use the slit-type or slot-type opening. However, the slit-type and slot-type openings are flawed, resulting that opening type of the blue metal mask in IGNIS pixel arrangement significantly affects further improvement of opening ratio of the sub-pixels and PPI.
In addition, in the organic light emitting display device, generally the opening ratio of the sub-pixel will be decreased with the enhancement of the resolution, finally leading to enhancement of work brightness of monochrome device and shortening the life of the display.